1. Field of the Invention
The present invention relates to fitting contact lenses on a patient for correcting presbyopia, and more particularly to a system and method for optimizing prescription selection based upon direct feedback from patients undergoing eye examinations and contact lens fitting utilizing a set of interactive simulations designed to demonstrate the impact of balancing near, intermediate and distance vision correction.
2. Discussion of the Related Art
As individuals age, their eyes are less able to accommodate, or bend their natural or crystalline lens, in order to focus on objects that are relatively near to the observer. This condition is known as presbyopia. More specifically, when an individual is born, the crystalline lens is pliable which makes it capable of a high degree of accommodation. As the individual ages, the crystalline lens gradually becomes more rigid and thus less able to accommodate. Similarly, for persons who have had their natural or crystalline lens removed and an intraocular lens or IOL inserted as a replacement, the ability to accommodate is absent. Although the intent of an accommodating IOL is to address this potential shortcoming, current accommodating IOL designs and concepts are relatively new and continue to evolve without providing a complete and satisfactory solution.
Among the methods used to correct for the eye's failure to accommodate is a method known as mono-vision in which, in most cases, a contact lens for correction of distance vision is utilized in the lens wearer's dominant eye, which is known to predominate for distance vision, coupled with a second contact lens for correction of near vision being utilized in the non-dominant eye. Mono-vision provides for both near and distance vision while allowing the brain to compensate as how the images should be construed. Mono-vision has limitations secondary to a decrease in binocularity. Another known method for correction of presbyopia is to use bifocal or multifocal contact lenses in both of the individual's eyes. There are many forms of bi-focal or multi-focal contact lenses for the correction of presbyopia. These design forms include concentric rings and aspheric designs, both of which may be designed for center distance or center near. All of these designs function by providing a range of powers within the pupil of the eye. For example, a concentric ring design may have a central ring that provides powers that are nominally equal to the power required to correct the distance vision of the subject, an adjacent ring that provides near powers, and an outer ring that also provides distance powers. There may also be fitting strategies to address intermediate vision demands between near and far distances, for example, computer screen viewing. Use of bifocal or multifocal lenses in both eyes results in a reduction of image contrast and resolution compared to mono-vision but usually maintains binocularity. Yet another method of treating presbyopia is to place a bifocal or multifocal lens in one eye and a single vision lens in the other eye. The disadvantage in using this method is in the large number of lenses that must be considered in order to provide the individual with satisfactory lens performance and the limitation of binocularity at near distance.
As may be seen from above, there are numerous solutions for the treatment of presbyopia and no single concept may be ideal for all individuals. Fit guides and tools are available to eye care specialists/professionals to help in selecting a starting pair of contact lenses. Some of these tools also help with more complicated calculations such as vertex distance and spherical equivalent, but none have a patient interactive segment that would allow a patient to see a simulation of what the contact lens solution could provide to them. Accordingly, there exists a need for an interactive fit tool that would allow an individual to be able to get a sense of what their vision would be like under real world circumstances and to select a desired visual experience prior to being fitted with a set of contact lenses.